Process of treating lubricating oils with selective solvents



, Patented June 22, 1937 UNITED STATES PATENT OFFICE PROCESS OF TREATING LUBBICATING OILS -WITH SELECTIVE SOLVENTS James M. Whiteley, .lr., Roselle, N. 1., asslgnor .to' Standard Oil Development Company, a corporation oi. Delaware NoDrawing. Application October 18, 1933, Serial 1 4 Claims. (01. 196-43) such as lubricating oils obtained from petroleum or from a primary tar or from a hydrogenated coal product; etc., with a selective solvent which is liquid or solid at ordinary room temperature and pressure. The improvement consists in carrying out the treatment of the oil with the selective solvent in the presence of an indifferent organic solvent which shows no special selectivity toward the various components of the oil if used alone and preferably is miscible in all proportions with both the oil and the selective solvent at the treating temperature. As examples of such indifferent organic solvents, we may mention aromatic hydrocarbons such as benzol, toluol, xylol, naphthalene, dimethyl naphthalene, further carbon disulfide, propyl ether, ethyl ether, etc. I

3 have found that by carrying out the extraction with the selective solvent in the presence of an indifferent organic solvent the process is greatly improved, not only as regards selectivity, but also 7 from the viewpoint of ease of handling. working temperature, solvent recovery, and lack of emul+ sificationtrouble.

The case of the extraction of Pennsylvania lubricating oils with phenol will illustrate in more detail the advantages which are obtained-by the.

Pennsylvania lubricating stocks with phenol it isT-E- found that these stocks are not miscible with the phenol until temperatures above -l00 C., arereached. Benzol is miscible with both the oil and the phenolin all proportions, Therefore, it distributes between the two layers when added to the mixture. It lowers the melting point of the phenol to 19 C .;so that working temperatures between 19 C. and 44 0., for example. can be used as well as temperatures above 44 C. The benzol lowers the temperature of operation so. that Pennsylvania lubricating stocks can beextracted at 25 C. with ease. If it is desired to lower the extraction temperature still further, a small amount, say 3%, of naphtha may be added. The

amount of benzol in the. blend determines the extraction temperature. The benzol does change the selective power of the phenol. The same yields and oils of the same quality are pro-.' 0 duced with the same amount of phenol. The

not

benzol is actually an inert diluent. The solvent recovery is not dimcult. The benzol and phenol boil far apart from each other and from the lubrieating oil stock so that they can be separated by simple distillation from both the solvent layer and the oil layer. Neither solvent is decomposed by heat, nor has any eifect on the oil treated.

The case of heavy tarry stocks serves to illustrate certain other advantages of the present invention. Such stocks'when treated with a selective solvent form bad emulsions. When, however, the extraction with the selective solvent is carried out in the presence of an indifierent organic solvent, the latter dissolves in the oil layer and lowers its viscosity so that no emulsion trouble is encountered. 4

The inert solvent, to give the best results, should be structurally similar to the selective solvent, the main difference being that the se-' lective solvent contains oxygen while the inert solvent does not. For instance, benzol is similar to phenol in that the phenol is made selective by the substitution of an OH group in benzol. The

' The solvent layer consists of selective and inert solvent and also contains the extract which has' been removed from the oil. The oil layer contains the rafiinate together with a certain amount of dissolved inert and selective solvents. The two layers are separated from each other and the solvents are then removed from both layers by distillation or by other means known in the art.

The treating may be carried out either in a batch processor in a continuous process which may be countercurrent. Very often several batch treat-' -=;ments are used-in succession according tov the countercurrent principle.

The inert solvent may be admixed with the solvent or part of the inert solvent may be added to the, oil. The latter operation is especially advantageous when the treating is carried out in a continuous countercurrent operation. This ,has 'twoadvantages: (1) The oil feed is made .less viscous and better extraction is obtained,

and -(2) the equilibrium condition at the feed inlet of the system is attained much more quickly since the tendency of the entering oil to dis? nitrobenzene,

methyl cellosolve,'etc. which have a high miscibility temperature with the oil; This miscibility temperature is lowered due to the presence of,

' the inert solvent and consequently the extraction may be carried out at or around room temperatures.

The following examples will illustrate the invention.

An oil of the following inspections had the following miscibility temperatures with phenolbenzol mixtures This oil was extracted with a solvent containing two parts phenol, and one part benzol at 27 C. to a countercurrent column. Five hundred parts of oil was extracted with 1000 parts of total solvent. The rafiinate was obtained with 78% yield and had the following characteristics:

Saybolt vis/ F 492 Saybolt vis/210 F -L 67.2 Gravity A. P. I 30.8 Viscosity index -1 110 The extracted material, 22%, had a viscocity of 126 at 210 F. and a viscosity index of 58.

As a second example, Pennsylvania bottoms oil dewaxed had the following viscosity characteristics and miscibility characteristics:

ViS/100 F v4137 ViS/210 F 237 Viscosity index 011 Phenol Benzol 1 -1 1 are.

When extracting this heavy oil, .an attempt was made to add an equal volume of benzol to the feed oil and extract with a solvent containing 3 parts of benzol to 4 parts .of phenol at 25 C. in a countercurrent column. The feed oil dissolved in the solvent completely so that another run had to be made using only 10% benzol in thefeed oil. Three volumes of oil was extracted with 10 volumes of total solvent containing 6 volumes of phenol and 4 volumes of benzol.

\ The raffinate and extract obtained were as follows:

Other experiments showed that the selectivityof the phenol is not adversely aifected.

The present invention may be modified in various ways. Thus, for example, a mixtureof several inert solvents may be added to the selective solvent in order to obtain the desired. re-

Equilibrium was easily set up.

sult. Other modifications will be apparent to those skilled in the art. 4

The invention is, therefore, not to be limited by the data given in the examples for illustration but only by the following claims in which it is my intention to claim all novelty inherent in the process.

What I claim is: v

1. In a solvent extraction of lubricating oil wherein a selective solvent, capable of selectively dissolving non-parafllnic constituents of said oil,

is passed into the upper portion of an extracting zone and the oil to be treated is passed into a lower portion of said extracting zone-and the undissolved constituents of said oil pass in countercurrent contact with said selective solvent and are withdrawn from the upper end of said extraction zone whereas the selective solvent and oil dissolved therein is withdrawn from the bottom of said extracting zone; the improvement which comprises carrying out the extraction process with a selective solvent having a high miscibility temperature in the presence of a nonselective diluent capable of reducing the miscibility temperature of said oil and solvent, add-' ing a portion of said non-selective diluent to the fresh oil to be treated in an amount less than the amount of oil being treated and adding additional non-selective diluent to the selective solvent introduced into said extraction zones.

2. In the solvent extraction of lubricating oil wherein a selective. solvent, capable of selectively dissolving non-paraifinic constituents of said oil, is passed into the upper portion of an extracting zone and the oil to be treated is passed into a lower portion of said extracting zone and the undissolved constituents of said all pass in countercurrent contact with said selective solvent and are withdrawn from the upper end of said extraction zone whereas the selective solvent and oil dissolved therein is withdrawn from the bottom of said extracting zone; the improvement which comprises carrying out the extraction process with phenol as the selective solvent in the presence of a non-selective diluent capable of reducing the miscibility temperature of said oil and solvent, adding a portion of said non-selective diluent to the fresh oil to be treated in an amount less than the amount of oil being treated and adding additional non-selective diluent to the phenol introduced into said extraction zones.

3. In the solvent extraction of lubricating oil wherein a selective solvent, capable of selectively dissolving non-parafllnic constituents of said oil, is passed into the upper portion of an extracting zone and the oil-to be treated is passed lnto a.

lower portion of said extracting zone and the undissolved constituentsof said oil pass in countercurrent contact with said selective solvent and are withdrawn from the upper end of said extraction zone whereas the selective solvent and oil dissolved therein is withdrawn from the bottom of said extracting zone; the improvement which comprises employing phenol as the selective solvent, adding benzene to the fresh oil to be treated in an amount less than the volume of oil being treated and introducing additional benzene into said extracting zone.

4. In the solvent extraction of lubricating oil wherein a selective solvent, capable of selectively dissolving non-parafl'lnic constituents of said oil,

is passed into the upper portion of an extracting zone and the oil to be treated is passed into a lower portion of said extracting zone and the undissolv-ed constituents of said oil pass in countercurrent contact with said selective solvent and are withdrawn from the upper end of said extraction zone whereas the'selective solvent and oil dissolved therein is withdrawn from the bottom of said, extracting zone; the improvement which comprises employing phenol as the selective solvent, adding benzene to the fresh oil to be treated in an amount equal to about 10 percent of the volume of 011 being treated and introducing additional benzene to said extracting zone in amount not in excess of the total phenol employed.

'JAMES M. WHITELEY, JR. 

